SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '861e68892c0e3bd380a4aae73eb9b1665868ee532998169f431f7ff248c1b379' 
  AND token = '9vkZAKerDUXzuhM3Qj0MVW1lPeENJB3qsEWMbgEkZuQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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