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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e86949c1a7d42c2b00336a48299667d0b9256449094d16e239c3e401a97c5889' 
  AND token = '+/EFzsmQ8DxzBZYelifVr1Feslttthq5lC/v46k9Gqk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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