SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b314205de0e4225a4844ee138cfd5db781df955c01c534c784a4f2de4c521e18' 
  AND token = 'b88y5PYVXruR+bVGBs77BbUnIPDyobyEfe0CvMrzZFw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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