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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd79857b211d24699c540ee34ab6337f952f14d2d2e054e3f1487120123a50038' 
  AND token = 'HuVOJmztNWpM5sJWnUE7o31+bMHWN74i2cY/qir97cM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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