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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3c3ccdf24ffb4924667d35462a25230e87b6d35b2561eede0a438a97684bbb24' 
  AND token = '1OQPgcbJgDyBAAYYJxyEmJXkOY3O71r0ri0KamDecqk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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