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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a81b89d59b4578ec2375e1ae4b29220f470db226dcd3b82c1dd646044b9f439d' 
  AND token = 'QwF8gK7Vw4cGOjndiGSyeGn89rdnnCXy54RYHfeD+ro=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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