SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '16ecade2fc849db043a02f21299c2e2bb5cfdfeca094f1395e7eb39a31c6c99b' 
  AND token = 'xqWkSWA4I+bdLdTs7mqPJne+aHaiMfIXT3dCUqcRk3Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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