SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe99b27a60d487505d80b0b988a35dfe660613c46e5827b596a0907261c14d1c' 
  AND token = 'l+QpViEVqPNSnFFilYCao4F5Qwo1jtbOaQzpv2BVZGw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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