SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '20e3f5d5c3cc207bbc7b0e6fd49f297f373aa2cabe5437deaf3112b3d21a8e23' 
  AND token = 'c4leGvSQ/fDmRPBsWF2uF/55Ts4U/WE+BhhNsyXNfyY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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