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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af3b37e7676de5968dfd0200fb140598772e96fc147da382ee2a2398801cce5f' 
  AND token = '6EZmdHIdmGRpJcJ1+M+kgpaOr2Qd+Lj39x7r0ERlRGA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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