SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '280c996b5b14986ade8b43763f2ecbdcc577888514cefc38339640894e2d53ac' 
  AND token = 'NfxFOk5nXWoTKHEB48AXMuk4VtxRrMJwmBidSlIn4PY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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