SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b71ed9fd6969017f1f84e6c3f2312554da3cf7672df9811244bb4d56b25bdd77' 
  AND token = 'VQOZvBl+npOsgqWc5mCG8g44UVuuudOBCrp8VcVAFkc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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