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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '338e08a377e09e4b92d562c8f41da39e50cf113547e487343bbacd685bc70964' 
  AND token = 'g8Dvugf+xwF8p/X81yZRFbTttv6fEZINslwvxQFY2kk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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