SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe85fa4410c87b131ba5f221babeba1df405a1b18ccf58524adec0d7a18c9a94' 
  AND token = 'JqZeW3y94CuXR2WGYPsQ/oxjuM7p2qYl/i2P3dpTDS8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}