SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b661b375478765f7b63fed978d16726f61d2442f3277376cc4a08320e60f2473' 
  AND token = 'xkPoMeIDcaSTjTYJg8sCIPjRZSMKr/jhracwMZ4PHh0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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