SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81191c8b2520da955829123138ee891d508df90afe7684bbda7b7d641d1183c5' 
  AND token = 'Zl0CGuhYX80AQOpZzi615KpIbht0vv7gIBRxguZFNUQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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