SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a76ab791a915e91fcdfe280a38cc38cdd73f6fb859475cd303248e4e65a85d78' 
  AND token = '4MkmbsqBhdnAfYByQ5K6Q7kp9pRtGmZFGUY9qnv0i/k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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