SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b297b51ea5f8fdd2a2c7236991e32a295f1bfcc2d43e0237b3212053d2629d3c' 
  AND token = 'Hq0qwrv4RyjugXr9ij4p5Hdt5qApW1/SnkVXKuUAJNo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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