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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '621b0f4abeb203348e2d467353fbe2088bad35cb9f7c9fd244bb384a8913c9e8' 
  AND token = '/tPLsbtZfJQBFc0qOwM9K7dnhtgyvtnalvDPXn4m84w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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