SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8396587363ebe783ede7070452b9fc1a5d488188f7190f52f6e67e6a00d56743' 
  AND token = 'yB0zeWnOD2UmWlh5kwrr0/VQSQOgZ4GR1d4jWqVx9xg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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