SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3b48244b9018288e45b617400c12e52d82c02d3fe918669e6eb741a07db0970' 
  AND token = '1J+3gi1CQLatBI2r8yTFk1fC7iy4SnLo3qbWQA5NmxE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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