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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '279e313fa01d2104581400f7f16657e44b3385195921a40fb1ed541212740e3f' 
  AND token = 'v+6aXKftD+Y34/e5QgakZ31T3+KkSpobkz6NQe5kuVY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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