SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '771a7f6c95d63ddc5ae975184c1e00876eaf3ead33cdebda8ee0fed037378abc' 
  AND token = 'g2o1/RwDenyL3lcAvBg2Ib6hHdbzlTiEaqMotb2757s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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