SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68cdf75389ebf91f3845d4840e052c25e7395a2cc836285e86a0de33686c3720' 
  AND token = 'XrjndFt89Ep241BYcHKnBqzIb4IYwSydCXAPAIlBBKU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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