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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3976903f81337b1bb5dd0f54c8aa3d21c765a9589c5ec3acf1a343fecc9c8b7' 
  AND token = 'pB6cuLbcVIrcZFDcgCmNVgmxyc9KSvFqiC30kE7MfuA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}