SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac6259577b54023b02db262d379b695941161f248eddb192c43779ef2d0389c9' 
  AND token = 'mCnKtuPzAlhNV2CQy9RGzprSbha0xVuFT2AHqBkTDQ0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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