SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bbc8588550f8d15702474a1fc36e10f0c88cb72e478923868f1280bdeb87828a' 
  AND token = '21vGITRPc/JUNiHsM3S9yejDl2mXqxZSjIjVVkTWrDs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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