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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd509a8f7cf7fa649c71d484cd236230a2d98ea0351523b16958b682e56ea3d97' 
  AND token = 'cjIFw6YnBxNM2pvXK1HOTE5dOyGMd4D3yLqgygkY+dg=' 
  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"
    }
  }
}