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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ddef8e2fe193305ca69b71355bffc8fc9be7f4bc447873b7e3d3d5d38ee3276b' 
  AND token = 'Q/UwOlSdGBRbUd7AnA8pzn5tAQubG3D9WlCebQ/uttY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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