SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '84637964a504e9fc4230a7da7f473c8480fa4ded10d5a35b21f36949dce53b73' 
  AND token = 'rgQncNAfqANSnYFwVOijBbiauWDtzMC+hP6+Z7Xzql0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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