SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fd8803c7a8b732ed961ab94c6a42a8c721a6cdb436cb783138969c921589f31' 
  AND token = '9uYAHJx33ZFyS1J3h4Fz1i2CdW949V1uBiiNe4/cQxU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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