SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51e5315364d331a7f91966386e94fe9861af8ff82a0c772af4a2a4b8370915be' 
  AND token = 'mws46Mij/FZRljKsMoWjTjxkfxN8JINZO/g8PAksjN0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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