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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21aa0ecb6cb56f2e8bceac5f2b53c58b57b19533cbfb17a0f3c358fa25b8a449' 
  AND token = 'GOCUKa+r+Vplqc0+T8PQ9WKS+3y2LDTTxVMkARnk8lE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}