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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7bb9f41cac07b6d3c49269de63d2ee9f8c08d4d009a5b7f7e24c9f040cd04e0' 
  AND token = 'N+i5wpAEHRZ2fwW9NvKO6K6wTSD5SRAdzRZAUcrioDc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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