SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8b7e041a24add3f0fcbe3a6295295d8494f4f06afab21e17227abbc9b67d975' 
  AND token = 'LodCR1tj29CCWNF+SsyBFLHm0dcFEffL4RDCEhRwSm8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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