SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc03fd9fc679a101cd02dab102a000d348fb5005f0eedf0482adc49198fe28d3' 
  AND token = 'uogMSQcReAf990Fj2aFKNO3VAuBu/lDq1oSWLmEWRjA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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