SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '852b4cc74a2f57e6bb58d398a26891a99e96caa7bfef7809a6ff69be7f992588' 
  AND token = 'sO+iFBDGZrrp9jeAKrcB36jKpmHNuRvB/a+4wiPsqU0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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