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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '371b74d942e63bcdcc55b1282e4308465efa55d134aa1536dce64e53042b9ce6' 
  AND token = '3E/3n2NpckcBs+ZE4PV5GF49mQG22R2lXMc4crqSFLI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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