SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e7c2bbbbe9f24da456fd2abd22309432cfd5451167256ad1ff017d9a92993d1' 
  AND token = '0BRj/imu4XBPVwqHjr9n2agmhEM4dlqtAQJSqCOWjhs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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