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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff90429ed1cd4ba6c8735c119d0b0caac9c36d928a95fb610675ba52d6aa45aa' 
  AND token = 'mgukaZJn1+aCXwUtbe/n7Wel6mGDKG5FCbBpPtB0+4A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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