SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b1bc1ff43b3d083914bbc58637a2f0d5fcddde8e0e718636b45fca4918f128' 
  AND token = 'RKshrJI7rIBzVPZVqyBCNPQjj6+r5lgwgplThU31si0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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