SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e923de200d019b358fd801282a079e861e29e0b19d8177877d98e9b69019fd24' 
  AND token = 'KCD+5zXP3a7zL9UDeTEfY7f0gxwhsY0Sblq8YDnfWE0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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