SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c84d04618507cff2a2e512d1be0304388db2904b546d370548517f75d9af109f' 
  AND token = 'WiGp+StVuvj3q/o2hyOMmsGNcOhHPMHNNuN/+ODsbGk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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