SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a757695ce0e16a414ea17868c41f4b256776614d7697e4503af0a2331a02afbf' 
  AND token = 'FQP8USLS58VXLD8xO7pRlYGmMYBPEXCeubxiJf6U7KM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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