SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '198034c573d752058e9a58da27288edec0c88519b055677ac1bf143484f2b42a' 
  AND token = '6vHptIia8z1VdFH3R0FjbdCePHep4/ibHXI3JFL3TBM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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