SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21c7da66f9e6d49b5b3a169bf1b8409976fdfb87848302e4677fe15f2dca9f3b' 
  AND token = 'owguU9xp7XLA4zFZKB1JnJo9miUOR+C/pCdct16N1YQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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