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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3c0b9f274d4e94ccf2bb50276a11fb2ca7c335c32c912c5880d5cfd09afdaf9' 
  AND token = 'R/d5l0k+imzaqPujBdVr1s4bygrUjovQLV2Lt1dKTsA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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