SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51e40728b71344700c1b3edc38ccd208231a6bde7732b321ff1c68873d67d113' 
  AND token = '7LZgeoyS1r1MQsw+kSuhI5STqprQFIoRWwAE0Ys7DKY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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