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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6d0f4dc2b75cb631242f4404699300090b9117bd7431bb3c6eda6a3f87aa2a0' 
  AND token = 'Istb5i4JbKq6USxa1riNs4a/EPlkKeD12L2q9ZD4Jaw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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