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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e67d6515785a4909cde56c62bf41c1a71ddd830d4a90f2eb396b8e2b6c21b3e0' 
  AND token = '/x5zrlPNjuq0LlJ1uq7cWeCMt+IOYbz3n9vAr02wwtg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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