SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21e66987b8271e4e209b7604a25de2490ba826c17cb8f1763d1b28cbb66addf5' 
  AND token = 'ThUVftSHwWDTAMPKSIhb5vpiLqv43DVbGjAij/DFLXw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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