SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c16086549825d224a0992bf1b89516da51059f494d67904cd732c4dda2c5a341' 
  AND token = '473+nqukSzzfjWJb4xGKm55oeF1IQsPBxQ9d2Q0Vg6E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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