SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c58c6f9e1259a13d483eda9df2081888f8aee7d4883941ab560a06f363fdbddb' 
  AND token = 'HS5XYstY89Eew65RnRjzOhvEcfnohoMNqvRImWc58Jg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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