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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b3ad3bd299745a03d016ba983eb1791b65d50668343b78c45ad63431ec187d98' 
  AND token = 'PvdKhdwqpaX8p5QRcAa5eR3TKdJnpUaepoIu1TcG7EA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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