SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b1122f6e16cb826ce89b8cba23d5b2a951646fa28ca46595b10aed1685b5508' 
  AND token = 'cXOpJkMjrvYMmXsey/rDRrgmKG+UTiJbMO6UgLxSwlA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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