SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cbf8794a33fd8468a0a465fd66b16609090c497c8c86e3624a0f9b3b828c56b8' 
  AND token = '77ZzUCGfzaYPeKNk/Vm5aUBAwmEKDY4jFMzqwhcdwoQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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