SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd1a20e4b2517a88c6b3f32069ecc0b43eaf5d289641a80e043e891bc3d4b1747' 
  AND token = 'OHmrAro6YXpkDaa1Ij2Ji4vxAI3xPN+bd7OFpwENIWM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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