SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '94e50da9308bb98beb0f9328fa0bc2c1eacee4b157eeaa1b857a514a7f084298' 
  AND token = 'UaQ4k3Gn/Gemc0lm6eHkczlMb5WpoeHJTBVme7hbnPQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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