SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6c1a55bb83142613a638d603958505f5b7ebfc996075f3d7e8a1c72e66aec19' 
  AND token = '6/psOwXILcevdvvrZypM8m4BxVHbYRwAj0AVLkVQV4A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}